1. Field of the Invention
The present invention relates to an Internet telephony gateway and a method for operating an Internet telephony gateway.
2. Background of the Related Art
Generally, an Internet phone means interactive voice conversation between personal computer (PC) users through an Internet Protocol (IP) network in real time. Demand of the Internet phone is on an increasing trend owing to its inexpensive communication fees. The Internet phone is divided into a PC-to-PC type, a PC-to-phone type, and a phone-to-phone type depending on communication means.
Up to now, various examples of the PC-to-PC type and the PC-to-phone type have been developed.
Meanwhile, the PC-to-PC type transmits and receives voice data through a mike and a speaker by connecting corresponding PCs with each other. This PC-to-PC type is implemented in such a manner that both PCs access to an IP network at the same time. Analog voice signals received through the mike using one program are digitized between the PCs, and the digitized data are compressed to obtain packet data.
When the packet type voice data are transmitted to an opposing PC through the IP network, a corresponding PC restores the packet type voice data and outputs an original voice through the speaker. The PC-to-PC type that enables communication as above has a problem in that both PCs should be accessed to the IP network at the same time using one program.
Meanwhile, the PC-to-phone type is implemented in such a manner that after a predetermined program is installed in a corresponding PC, both a PC and a phone are accessed to the Internet and then linked to a public switched telephone network (PSTN) through an Internet telephony gateway installed in a specific area. Accordingly, the PC-to-phone type enables communication using a phone. However, the PC-to-phone type has a problem in that any one of the PC and the phone should be linked to the PSTN.
A related art Internet telephony gateway and a schematic network for Internet communication services will be described with reference to FIG. 1.
As shown in FIG. 1, a corresponding Internet telephony gateway 100 is linked to either a PSTN 50 or an IP network 60. Subscribers of either the PSTN 50 or the IP network 60 can perform communication through the IP network using terminal units such as phones and computers.
The Internet telephony gateway system 100 uses either an E1/T1 grade R2 signaling mode or a Link Access Protocol for D-channel (LAPD) signaling mode as a signaling mode for call control setup with the PSTN 50 or the IP network 60 linked thereto.
The R2 signaling mode also known as an ABCD signaling mode is operated by number 16 of a time slot in case of E1 grade. The LAPD signaling mode is to form packet data of signaling data with a D channel protocol of an Integrated Service Digital Network (ISDN) so as to control the packet type signaling data.
However, in the Internet telephony gateway 100, a point, where a defect is detected, is subject to the IP network 60 or the PSTN 50.
Therefore, the presence of any failure in the connection state between different networks is processed by time out due to polling. In this case, if any failure occurs in the PSTN 50, the abnormal state is maintained until a subscriber terminal unit of the IP network is restored by itself.
Meanwhile, if any failure occurs in the IP network 60, the abnormal state continues to remain until a subscriber terminal unit of the PSTN is restored by itself.
As described above, when one terminal unit is in failure state, the other terminal unit does not receive any notice thereof. A corresponding user of the other terminal unit is merely in standby state for a predetermined time. Moreover, the corresponding user must pay communication fees corresponding to the predetermined standby time. Accordingly, the related art causes subscribers loss in both time and economical aspects.